Ground Settlement - Managing the Effects of Tunnelling

Settlement is the technical term given to the way the ground moves around a hole after it has been dug out. Digging tunnels, shafts and basements always causes small movements in the ground.

This is true of Crossrail’s tunnelling works and significant effort was made to limit the effects of this movement on buildings that sit above our tunnels.

Our work was conducted to create as little settlement as possible. We did this firstly by controlling the way that we carried out the tunnelling and then, where necessary, by treating the ground so that it was less likely to move.

One effective way of treating the ground is by using ‘compensation grouting’.

During construction extensive use was made of compensation grouting, a well-established technique employed on tunnelling projects around the world to minimise settlement. It works by injecting a cement-like substance, called grout, into the ground to firm up the area where settlement is expected to occur. Find out more about Crossrail’s grouting programme.

Even with these measures, some level of settlement was inevitable although the amount of settlement on the Crossrail project has generally been lower than anticipated.

Our approach to dealing with buildings affected by settlement is set out in Crossrail Information Paper D12 - Settlement. This includes a commitment to repair damage caused by Crossrail Ltd works.

In line with this policy we surveyed thousands of properties near our tunnels before tunnelling started. These surveys, known as pre-construction surveys, allowed us to record existing defects.

Now that ground movement resulting from our tunnelling works has stopped we are in a position to conduct follow up (post-construction) surveys if required and to understand whether the Crossrail Ltd works have caused damage requiring repair.

If you believe that damage has occurred as a result of the Crossrail Ltd works then you may also be entitled to a post- construction survey in line with our settlement policy. You may also be entitled to submit a compensation claim. This should be suitably detailed to enable our engineers and loss adjustors to make a valid assessment of the claim.

To request a post-construction defect survey or to file a claim you should contact our helpdesk on 0345 602 3813 or [email protected]